Engineers and scientists have designed microelectromechanical systems (“MEMS” or “MEMS devices”) to perform a wide variety of functions. Among other things, such devices can sense acceleration or rotational movement, redirect light data signals between optical fibers, detect pressure changes, or transform an acoustic signal into an electric signal. These diverse devices commonly interact with their internal microstructure (e.g., detecting microstructure movement or actuating microstructure) using electrostatics or piezoelectrics.
MEMS devices using piezoelectrics to detect movement (e.g., an accelerometer) can employ a bimorph structure as a spring to support its corresponding mass above a substrate. Specifically, by way of example, FIG. 1A schematically shows a part of a prior art accelerometer 10P having a bimorph spring 12P supporting a mass 14P above a substrate 16P. As shown, the spring 12P has five distinct layers; namely, a middle electrode 18P between top and bottom polarized layers 20P and 22P, and two exterior electrodes 24P and 26P respectively on the top and bottom of the two polarized layers 20P and 22P. The two polarized layers 20P and 22P have the same polarity at rest.
Movement of the mass in the positive Z-direction, which, in this example, is generally orthogonal to and toward the substrate, causes one of the polarized layers 20P or 22P to compress while the other polarized layer expands 20P or 22P. This causes the first and second polarized layers 20P and 22P to have the electrical pattern shown in FIG. 1B (schematically showing the spring 12P only). The strength of those electric fields is a function of the compression/expansion of the respective polarized layers 20P and 22P. A signal detector 28P connected between the middle electrode 18P and one of the exterior electrodes 24P or 26P detects a degree of change in polarity, indicating qualities of the movement of the mass 14P.
To the knowledge of the inventors, many in the art consider this design to operate satisfactorily. In contrast, the inventors believe that future technological demands may limit the applicability of this prior art design across many current and emerging applications.